Insulated connector



INSULATED CONNECTOR Filed Aug. 30, 1955 7:" I j I j &'\' r20" KIHJ.

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Michael F. OKeefe and Carl B. Hamlin United States Patent INSULATED CONNECTOR Application August 30, 1955, Serial No. 531,336

1 Claim. (Cl. 339-276) This invention relates to insulated electrical connectors of a type adapted to be cold-forged onto an electrical conductor. In certain respects it constitutes an improvement over the disclosures contained in Watts Patent 2,410,321.

Insulated connectors are well known in the art and some of the connectors presently manufactured consist of a plastic sleeve made from such materials as vinyl chloride or nylon, among others, encompassing a metal ferrule, thus serving to insulate the ferrule.

One of the diificulties with many of the insulated connectors presently available is that the insulation sleeves cannot withstand operating temperatures in excess of several hundred degrees. When extremely high temperatures are encountered, such as the temperatures present during the operation of some aircraft or guided missile devices, these terminals may break down-due to failure of the insulating sleeve. I

Other insulating sleeves capable of withstanding these high temperatures are not readily adaptable to a connector of this type since no satisfactory means has been devised for securing them to the connector and holding them in place prior to and during the crimping operation.

Thus, it is an object of this invention to provide a connector insulated with material that will withstand extremely high temperatures.

It is also an object of this invention to provide a new means of binding an insulating sleeve to a metal ferrule.

A further object of this invention is to provide a secure engagement between a metal ferrule and the surrounding insulating sleeve.

An additional object of this invention is to provide a means for protecting the insulating sleeve.

Other important features and objects of the invention to which reference has not been made hereinabove will appear hereinafter when the following description and claimlare considered with the accompanying drawings, in which:

Figure 1 shows a plan view of the connector with the insulating sleeve thereon;

Figure 2 shows an end view of the connector shown in Figure 1;

, Figure 3 shows a view taken through section lines III--III of Figure 1;

Figure 4 is a perspective view similar to Figure 3 showing a modification of the connector; and

Figure 5 shows a fragmentary view of an insulated covering secured to a connector wherein square-threaded or keystone serrations are employed.

Referring to the connector shown in Figures 1 to 3, a metal ferrule has one end 11 which is internally bell-mouthed to receive the bare end of an electrical conductor. The opposite end of the ferrule 10 has a tongue 22 capable of being secured to a binding post by means of opening 23. Thus, when an electrical conductor is secured to the terminal, such as by being coldforged to the ferrule 10, the combination of the ferrule 10 and the tongue 22 act as a conducting means convey- 2,807,792 Patented Sept. 24, 1957 ICC ing electricity between the conductor and the post. Of course the tongue may be eliminated and a second wire fed into the opposite end to connect two or more conductors together.

As shown in Figure 3, a corrugated surface 18 is provided on the outside of metal ferrule 10. An insulating sleeve 12 is secured by means of a friction fit to ferrule 10 and surrounds the ferrule and extends rearwardly thereof to provide complete insulation. This sleeve may be made of any flexible material, preferably of a type capable of receiving a crimp without tearing the insulation but not necessarily so. Illustrative examples include asbestos, fiberglass, fibrous or braided materials and plastics with good dielectric and high operating temperature characteristics. The insulating sleeve may be flush with the outer metal ferrule as shown in Figure 4, or may extend rearwardly thereof as shown in Figure 3.

It will be noted that the inside surface of the insulating sleeve 12 assumes the shape of the outer surface of the ferrule 10 thereby providing corrugations 20 on.

the inner surface of sleeve 12. The corrugations 20 mate with corrugations 18 on the ferrule 10, thus effecting a mechanical lock to provide an extremely secure connection between the ferrule and the sleeve. This provides a strong bond for holding the sleeverelative to the ferrule prior to and during the crimping operation. Again referring to Figure 3 an outer metallic sleeve 14 tightly surrounds the insulating sleeve 12 so that the metallic sleeve is concentric with the ferrule 10 and the insulating sleeve 12. The outer metallic sleeve 14 is constricted as at 16 preferably in the vicinity of the inner metallic ferrule 10 and the insulating sleeve may be flush with or extend past the forward end of the metallic sleeve 14.

In actual practice the provision of a corrugated barrel (even without the outer metallic sleeve 14) is effective to secure the sleeve 12 to the ferrule 10. This is accomplishd by the use of an interference fit between the sleeve 12 and the ferrule 10. Since the inside diameter of the sleeve 12 tends to be less than the outside diameter of the ferrule, when the sleeve is stretched over the ferrule, it will contract in the vicinity of the corrugated section. When the connector is crimped onto a conduct-or the sleeve is compressed into the corrugations to provide a strong bond between the sleeve and the ferrule. However, for reasons which will be set forth in a description of the operation, an outer metallic sleeve 14 preferably is provided.

As shown in Figure 3, because of the constriction, the outer metallic sleeve beans upon the insulating sleeve to form a pair of shoulders 24, 26 which engage the insulating sleeve 12. Furthermore, the constricted portion of the sleeve bears against the inner metallic ferrule compressing the insulating sleeve 12 therebetween to secure more firmly the insulating sleeve relative to the outer and inner sleeves 10, 14. In addition to the hold ing action of the outer sleeve, the pressure of the outer sleeve on the insulating sleeve 12 causes the serrations 2%] on the inner surface of the insulation sleeve 12 to become more pronounced thus providing a stronger bond between the sleeve 12 and the ferrule 10.

0peration.-When it is desired to crimp the connector to a conductor such as a wire, the bare end of the wire is inserted into the open barrel and the wire is thus positioned within the ferrule 10. Crimping dies are brought to bear upon the outer sleeve 14 at the constricted portion 16, in the vinicity of the corrugations 18 on ferrule 10. The crimping force deforms the outer sleeve 14 and is transmitted through the insulating sleeve to the inner ferrule 10, which is likewise deformed. The outer sleeve and inner ferrule are thus deformed so as to be urged into a. tighter engagement to provide an additional means for securing the insulation sleeve relative to the outer sleeve and inner ferrule. Since the insulating sleeve will permit a degree of compressibility, depending on the material to be used, this compression of the sleeve during the crimping operation will also aid in firmly binding the sleeve to the ferrule when the insulating sleeve is compressed into the ferrule 10.

During the crimping operation the outer metallic sleeve 14 beans the brunt of the direct pressure exerted by the crimping dies. This protects the insulating sleeve 12 from the dies and prevents it from tearing during the crimping operation. Without this feature when substances suchas asbestos, fiberglass, some plastics and other tough materials are used as an insulating material, the jaws of the die may tend to puncture the insulating sleeve during the crimping operation, thus causing dielectric failure.

Furthermore, the outer metal sleeve permits the use of an insulating sleeve without applying a bonding agent. The metal sleeve secures the insulating sleeve to the ferrule prior to and during the crimping operation and prevents an insulating sleeve from losing its shape when the terminal is used in applications at temperatures above the normal heat distortion temperature of the sleeve.

Figure 4 shows a modification of the device shown in Figures 1 to 3. Corresponding parts are designated by prime reference numbers. As shown in Figure 4, the tongue 22 of the terminal is offset from the ferrule 10' to accommodate the thickness of the insulating material in installations \vhere'the terminal is bolted to a terminal strip.

The outer metal sleeve and the insulation sleeve may extend rearwardly from the wire entrance back over the insulation on the conductor in either embodiment to provide an insulation support and also to prevent fiarshover between the conductor and the outer sleeve at this point. The insulation sleeve may be flush with the outer metallic sleeve (Figure 4) or extend beyond it as shown in Figure 3.

Figure 5 illustratesa further modification wherein the same reference charactens have been used as before,

but with the addition in each instance of a double prime. As shown in Figure 5, square threaded or keystone serrations may be advantageously employed to provide a strong mechanical bond between the inner fen'ule and the insulating sleeve. I

The front edge of the outer metal sleeve 14 (14) (14") may be even with the forward edge of the inner ferrule and the insulating sleeve extend forwardly of the outer sleeve, thus preventing electrical flash-over between the ring tongue and the outer metallic sleeve.

Changes in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only. The actual scope of the invention is intended to be defined in the following claim when viewed in its proper perspective against the prior art.

We claim:

An insulating electrical connector capable of being cold-forged onto a conductor including: an inner metallic ferrule having an uneven outer surface, a fibrous insulating sleeve tightly surrounding the ferrule with the inner surface of the insulating sleeve assuming the shape of the outer surface of the ferrule, and an outer metallic sleeve surrounding the insulating sleeve and having an inside diameter which is less than the original outside diameter of and in constrictive engagement with the insulating sleeve whereby the insulating sleeve is secured between the uneven outer surface of the ferrule and the inner surface of the outer sleeve.

References Cited in the file of this patent UNITED STATES PATENTS 2,379,567 Buchanan July 3, 1945 2,410,321 Watts Oct. 29, 1946 2,685,076 Hoffman July 27, 1954 

